Distinguish between recursive and non-recursive mappings: user can choose...

Distinguish between recursive and non-recursive mappings: user can choose whether a mapping is recursive or not via the new "Recursive?" column added to the mappings table.  Mappings are recursive by default.  Mappings from configs before the introduction of this distinction are treated as recursive.

The main motivator for this change is so that the mapping of gj -> j - very commonly used by Vim users - can be used without a stack overflow :)

CCBUG:314415

REVIEW:109962